fix: resolve executor compile regressions

[KooshaPari]

Summary

• Fix syntax/parsing issues in Kiro model mapping function.
• Remove duplicate GitHub Copilot execution session close method.
• Fix Codex websocket disconnect logger scope and drop unused sha256/hex imports.

Validation

• go test ./pkg/llmproxy/executor ./pkg/llmproxy/translator/kiro/claude -run TestDoesNotExist -count=0

[KooshaPari]

Superseded by #205 (merged) and follow-up #206. Closing to keep branch history consolidated on main.